In many cases, modern glass facades are not just a functional element of a structure, but in fact also serve increasingly for generating solar energy. Tailored solar modules make accurate integration into building grids and profiles possible. Semitransparent solar cells, but also opaque solar cells with transparent areas, make photovoltaic glazings appear to be flooded with light. Here, the solar cells often take on the desired effect of protection against the sun and glare.
The production of such photovoltaic systems requires operating conditions such as those which are conventional primarily in the production of semiconductors and integrated electronic circuits. In the production of photovoltaic systems, these so-called clean room conditions also additionally make it necessary to handle shock-sensitive glass sheets with a large surface area.
For the safe handling of such glass sheets, it is necessary to remove the sharp edges which arise during chipping to the required formats and to grind down said edges.
For this purpose, DD 129751 PS has disclosed a vacuum clamping apparatus for machines for processing edges of glass sheets.
Said clamping apparatus is based on the object of reducing the expenditure on time and work during the clamping and release of the glass sheets by corresponding vacuum control.
In order to achieve this object, said document describes a vacuum clamping apparatus for machines for grinding and polishing the edges on round and oval glass sheets, which is characterized in that a compressed air supply apparatus is connected to the vacuum clamping device and can be connected to a clamping plate by a line provided with a shut-off valve via a vacuum line and to a solenoid valve, which shuts off the vacuum line, via a line containing a shut-off valve which opens only temporarily. In addition, a contact manometer is connected to the vacuum line and initiates sequence control when a minimum vacuum is reached.
Apart from the measure of using vacuum control for clamping and releasing a glass sheet for the purpose of processing edges of glass sheets, said document provides no indication of the automatic grinding of edges of glass sheets.
Furthermore, DE 85 03 914 U1 discloses an edge grinding machine, which is based on the object of designing an edge grinding machine in such a manner that, when profiled circumferential grinding wheels are used, it is possible to set the required operational distance between the circumferential grinding wheel units quickly, without any problems and reliably.
This is achieved substantially by virtue of the fact that the distance between the circumferential grinding wheel units is fixed by end stops which can move in the movement path of the circumferential grinding wheel units, and that each circumferential grinding wheel unit is assigned a plurality of end stops, of which in each case one lies in the movement path of the circumferential grinding wheel unit.
This design has the advantage that no skill or special care is required whatsoever in the event that the distance between the circumferential grinding wheel units needs to be changed, since it is merely necessary to move a predefined end stop in order to move the corresponding circumferential grinding wheel units into the desired position.
Although this simplifies operation, it does not indicate a system for automatically grinding edges of glass sheets.
Furthermore, DE 32 31 895 A1 discloses a machine for chamfering edges of sheet-like workpieces, in particular glass panes, in which a grinding wheel arrangement is used to grind down at least one edge of the workpiece during a relative movement between the workpiece and the grinding wheel arrangement.
In the case of this machine, the quality of the chamfered edges should be improved to the effect that the grinding tracks which are clearly apparent in the case of prior art machines are reduced.
For this purpose, it is provided in DE 32 31 895 A1 that the grinding wheel arrangement has at least one circumferential grinding wheel, preferably two circumferential grinding wheels for simultaneously grinding two adjacent edges, and the axes of rotation of said circumferential grinding wheels are arranged substantially parallel to the edges to be ground during grinding.
This machine too is not suitable for automatically grinding edges of glass sheets.
Furthermore, US 2003/0181145 A1 discloses an apparatus for polishing the edge of a glass pane which is moved along a polishing wheel by means of a separate drive. In this document, a pressure subassembly is used to ensure that a predetermined constant contact pressure prevails between the polishing wheel and the edge of the moving glass pane. The waste produced during the polishing operation is disposed of. This known apparatus is not suitable, however, for the degrees of purity required in clean rooms.
In the case of a partially comparable apparatus, known from U.S. Pat. No. 6,099,385, for removing a protruding edge of a plastic lamination in a pane of safety glass, an apparatus for monitoring the wear of the grinding wheel is additionally also provided. This is substantially used to keep the contact pressure between the product for grinding and the grinding wheel constant and to compensate for the reduction in the diameter of the grinding wheel brought about by wear by means of an increased rotational speed. The extraction apparatus provided here serves for rough removal of plastic fragments from the plastic lamination which is ground down. Said apparatus is not suitable for grinding edges of glass sheets under clean room conditions.
A further comparable system design is known from EP 1 491 288 A1. This document describes specific methods for guiding a glass sheet along a grinding wheel using a robot hand. As a result, the accuracy of the chamfering obtained should be increased and the process time should be reduced. This document does not refer to the removal of the grinding dust, in particular under clean room conditions.
The special requirements for systems for grinding edges of glass sheets in clean rooms are therefore not taken into consideration in the prior art.